I've been playing with the new 'shape match' constraint in vellum, but can't work out how to dynamically scale them during the sim. Normal approach would be to animate rest length scale, which would let you make the simmed objects bigger or smaller. When using 'shape match' however, the rest-length is always set to 0, making any scaling redundant.

Is it not possible to animate these constraints?

Thanks!

- you can either animate v@rest point attribute on the ConstraintGeometry

- or use Vellum Rest Blend to make it match some reference geo

Fantastic, that works, thank you!

Hi there - I'm aware this is an old topic, so I apologize for reopening.


I have been unable to get the first option to work as suggested by Tomas (animate v@rest point attribute on the ConstraintGeometry)


I have attached a simplified build as an example -

I am sourcing geometries that are split into two groups (idGrp 1 and 2), which are then assigned different constraint properties based on their group at sop level.

One of the groups uses shape match constraints, but I'd like the Nage attribute I've created (based on @TimeInc) within the dopnet to drive the scale of the Shape Match ConstraintGeometry - I've created a 'stretchSM' group on the vellum constraint, which I'm referencing in the dopnet.

I don't want to use a shape blend, as eventually I'll be sourcing lots of different shapes randomly, and the first method seems the simplest.

Any help or further guidance would be much appreciated.

Thanks! - K

v@rest on ConstraintGeometry is a point attribute so your wrangle has to be set to Points

then your code:
would completely override it which would result in all points having the same value and therefore shape would be a single point
but even if you did this:
it would just scale v@rest from previous timestep, resulting in exponential scaling, which is likely not what you want either

one way is to store the original v@rest in another attribute like v@restorig, you can do it in SOPs or even generally create it on the fly in DOPs for pieces that don't have it yet

Thank you, Tomas

That 'if' statement is much cleaner and makes sense. Thank you for the breakdown as well, stupidly thought I needed to run on prims for this as I was working with constraints *doh*

Thanks!